C和指针 学习笔记-4.函数

參数传递:

參数传递採用按值传递

ADT&黑盒

ADT：abstract data type,抽象数据类型

c能够用于设计与实现抽象数据类型，由于它能够限制函数和数据定义的作用域。这样的技巧也称为黑盒设计

user.h

#define MAXLEN 3
struct UserClz {
	char *name;
	char *phone;
	char *address;
};
typedef struct UserClz User;
/*
*接函数
*通地名称查找地址
*/
char const * lookupAddress(char const *name);
/*
*接函数
*通地名称查找电话
*/
char const * lookupPhone(char const *name);

user.c

#include "user.h"
#include <stdlib.h>

#include <string.h>
/*
*限制訪问范围
*/
static User users[MAXLEN]={
 	{"user1","111","aaa"},
 	{"user2","222","bbb"},
 	{"user3","333","ccc"}
 };
void init(){
	int j=0;
	for(j=0;j<MAXLEN;j++){
		printf("\n");
		printf("name:||%s||\n",users[j].name);
		printf("phone:||%s||\n",users[j].phone);
		printf("addr:||%s||\n",users[j].address);
	}

}
/*
*限制訪问范围
*/
static  User const * getUserByName(char const *name){
	User const *pu;
	pu=users;
	int i ;
	for(i=0;i<MAXLEN;i++){
		if(strcmp((pu+i)->name,name)==0){
			return pu+i;
		}
	}
	return NULL;
} 

char const * lookupPhone(char const *name){
	User const *pu;
	pu=getUserByName(name);
	if(pu!=NULL){
		return pu->phone;
	}else {
		return NULL;
	}
}

char const * lookupAddress(char const *name){
	User const *pu;
	pu=getUserByName(name);
	if(pu!=NULL){
		return pu->address;
	}else {
		return NULL;		
	}
}

main.c

#include <stdio.h>
#include "user.c"
void main(){
	init();
	printf("phone=%s\n",lookupPhone("user1"));
	printf("address=%s\n",lookupAddress("user2"));	
	
}

以上就是黑盒的样例，墨盒的功能通过规定的接口訪问模块,接口函数lookupPhone与lookupAddress,

用户不能直接訪问和模块实现相关的数据,如:users，getUserByName，它们被声明为static

递归

求菲波那契数

#include <stdio.h>
int fn(int n){
	if(n<=2) return 1;
	return fn(n-1)+fn(n-2);
}
void main(){
	printf("result:%d\n",fn(5));// result:5
}

过程图